Volvo’s new electric supercharger

Perhaps you saw the news last week about an experimental engine under development at Volvo. It’s a 2.0-liter gasoline-powered four-cylinder that cranks out an amazing 450 horsepower.
At 225 horsepower per liter, it would be one of the most power-dense engines ever produced, if Volvo decides to build it.

How Volvo engineers boosted the output of the engine is ingenious. Two turbochargers plumbed into the engine’s intake system are powered not by exhaust gases — the traditional way — but by air pressure generated by what I would call a third turbocharger.

It’s not clear what that third device is — a turbo or a supercharger. From its appearance, it looks like a turbocharger. But the turbine on the exhaust side has been replaced with an electric motor. Volvo calls the unit an “electrically powered turbo compressor.” But French supplier Valeo, which makes a similar device, calls theirs an “electric supercharger.”
I say it is. What defines the turbocharger in my view is not its source of power but the method in which the air is pressurized. Superchargers are usually mounted directly to the intake side of the cylinder head, and air is blasted into the engine via rotors or air screws. Also, superchargers are connected to the engine mechanically, usually by a fan belt to the front of the crankshaft.

Turbochargers have two vanes inside that look a bit like the fan you see on the front of a jet engine. One side of the turbine is driven by exhaust gases and powers the other side, the impeller, which compresses the air and pressurizes the engine’s intake.

There’s no question that Volvo’s experimental engine uses two turbos to boost the air going into the engine. But is the device that is powered by the electric motor no longer a turbocharger because exhaust gas doesn’t power it?

Here’s why this is important: We might be seeing something like this in production fairly soon. Valeo’s “electric supercharger” is being tested by Audi. The rumor mill around Detroit says that the Valeo device will be offered by Audi in a regular production vehicle, possibly as soon as next year.
See more at: Autoweek


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